DESCRIPTION: Two circadian clock genes, period (per) and timeless (tim)have been studied intensively in Drosophila melanogaster. Recently, Reppert and colleagues have cloned a functional homolog of per in the giant silkmoth, Antheraea pernyi. Analysis of per function in circadian clock neurons in silkmoth brain suggests that very different molecular mechanisms underlie clock function in silkmoths. The applicants now propose to extend our analysis of clock gene regulation and function in silkmoths. Specific aim 1 will delineate that PER-expressing cells in silkmoth brain are circadian clock cells, by examining the effects of antisense oligodeoxyribonucleotide and light treatments on behavioral and molecular rhythms, and developing in vitro systems for ablation and localization studies of silkmoth clock cells. Specific aim 2 proposes to define tissue-specific mechanisms of per regulation by determining whether silkmoth eye contains a circadian clock, examining tissue specific isoforms of per, and defining PER interacting partners. Specific aim 3 proposes to examine the circadian function of a per antisense transcript by determining whether the per antisense transcript modulates clock function and cloning the DNA for the antisense transcript. The longterm goal of the proposal is to gain a better understanding of the cellular and molecular mechanisms that underlie circadian rthymicity. The proposed studies provide an integrated approach that will supply important information about defined circadian clock elements and their new mechanisms of action in silkmoths. Increased understanding of the fundamental mechanisms of biological clock function will facilitate the development of better treatment strategies for a wide range of disorders.